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<h3><a name="SECTION0016553000000000000000">
14.5.5.3 RotatingFileHandler</a>
</h3>

<p>
The <tt class="class">RotatingFileHandler</tt> class, located in the <tt class="module">logging.handlers</tt>
module, supports rotation of disk log files.

<p>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><span class="typelabel">class</span>&nbsp;<tt id='l2h-2913' xml:id='l2h-2913' class="class">RotatingFileHandler</tt></b>(</nobr></td>
  <td><var>filename</var><big>[</big><var>, mode</var><big>[</big><var>,
                                       maxBytes</var><big>[</big><var>, backupCount</var><big>]</big><var></var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt>
<dd>
Returns a new instance of the <tt class="class">RotatingFileHandler</tt> class. The
specified file is opened and used as the stream for logging. If
<var>mode</var> is not specified, <code>'a'</code> is used. By default, the
file grows indefinitely.

<p>
You can use the <var>maxBytes</var> and
<var>backupCount</var> values to allow the file to <i class="dfn">rollover</i> at a
predetermined size. When the size is about to be exceeded, the file is
closed and a new file is silently opened for output. Rollover occurs
whenever the current log file is nearly <var>maxBytes</var> in length; if
<var>maxBytes</var> is zero, rollover never occurs.  If <var>backupCount</var>
is non-zero, the system will save old log files by appending the
extensions ".1", ".2" etc., to the filename. For example, with
a <var>backupCount</var> of 5 and a base file name of
<span class="file">app.log</span>, you would get <span class="file">app.log</span>,
<span class="file">app.log.1</span>, <span class="file">app.log.2</span>, up to <span class="file">app.log.5</span>. The file being
written to is always <span class="file">app.log</span>.  When this file is filled, it is
closed and renamed to <span class="file">app.log.1</span>, and if files <span class="file">app.log.1</span>,
<span class="file">app.log.2</span>, etc.  exist, then they are renamed to <span class="file">app.log.2</span>,
<span class="file">app.log.3</span> etc.  respectively.
</dl>

<p>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2914' xml:id='l2h-2914' class="method">doRollover</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
Does a rollover, as described above.
</dl>

<p>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-2915' xml:id='l2h-2915' class="method">emit</tt></b>(</nobr></td>
  <td><var>record</var>)</td></tr></table></dt>
<dd>
Outputs the record to the file, catering for rollover as described previously.
</dl>

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<span class="release-info">Release 2.5.1, documentation updated on 18th April, 2007.</span>
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